a. Field of the Invention
The invention relates to hubs used for supporting data storage media and more particularly, to a hub collar construction for centering a hub on a spindle.
B. Prior Art
Disk recording media are used in the computer industry for storage of large amounts of data. The recording media may contain millions of bytes of data which are accessible to the computer by means of a transducer or reading head which scans the data as it rotates at high speed relative to the recording head. The recording medium may be a ferromagnetic material having magnetic characteristics which make it suitable for reading or may have optical characteristics which make it suitable for reading, or may have still other characteristics. However, in most instances the medium itself is somewhat fragile and although it typically rotates at high speed, the medium itself is not attached to a spindle. Rather, the medium is mechanically attached to and supported by a hub which in turn is connected to a spindle or other spinner mechanism of a motor.
One class of hubs is adapted for mounting on a rotating spindle by means of a special collar in the interior of the hub for centering the hub with respect to a spindle which fits within the collar. The hub must be accurately centered because data reading and writing transducers rely on the concentricity of the data tracks. While adjustments of the transducers are made by servos, the data tracks are centered at the geometric center of a hub which should have its geometric center coincide with the geometric center of a spindle, usually driven by a motor. A prior art hub is illustrated in FIGS. 1 and 1a of the drawings. The annular hub 11 has an annular collar 13 in its interior, for placement on a spindle. The geometric center of the collar coincides with the axis of rotation of hub 11 and a rotating spindle on which the hub is placed. Collar 13 is usually machined out of metal and is tightly pressed into place in the center of a hub.
In FIG. 1 an annular collar 13 of the prior art is shown by the dashed lines D to have been removed upwardly to show its construction. This construction may be seen more clearly in FIG. 1a. The collar 13 has an inside surface 15 and an outside surface 17. The inside and outside surfaces are in fact walls separated by a circular groove 16, which extends part of the way from the top to the bottom of the collar. The bottom of the collar supports the inner and outer walls. The inside surface 15 is interrupted at intervals by short wall portions 19, 21, 23 which project inwardly more than the remainder of the inside wall. The wall portions 19, 21, 23 form tangs which compressibly contact the exterior of a spindle for accurate centering of a hub on the spindle. It should be noted that the tangs do not transfer mechanical energy to or from the hub for spinning. Such energy is transferred by other means, such as by lugs or bolts which do not influence alignment of the hub with respect to the spindle.
However, as can be seen from FIG. 1a it is quite difficult to manufacture the collar shown. The inside wall has different circular diameters. The first and greatest diameter is formed by the main portion of the inside surface 15 of the wall, while other, lesser diameters are defined by the portion of tangs 19, 21, 23 facing the axis of rotation. The upper portion of each tang 19, 21, 23 has a diameter approximately one or two thousandths of an inch less than the lower portion thereof, which in turn has a diameter approximately twenty thousandths of an inch less than the main wall portion of inside surface 15. The construction of the collar 13 requires intricate machining, such that most of the cost of the hub is represented by the collar 13.